Los Angeles, California (CNN) -- U.S. authorities have discovered 30 tons of marijuana that were part of a smuggling operation using a tunnel under the California-Mexico border, officials said Wednesday.

The 600-yard tunnel -- which features a rail system, lighting and ventilation -- connects a warehouse in Tijuana with one in the Otay Mesa industrial area of San Diego, said U.S. Immigration and Customs Enforcement spokeswoman Lauren Mack.